A variety of bent wire spring units have been developed to replace coil springs which have been conventionally employed to support and connect a grid frame to a rigid base frame such as a box spring assembly commonly used for supporting mattressess. Such bent wire spring units are shown in U.S. Pat. No. 4,218,790 and the patents cited therein and are generally comprised of a single or multiple lengths of wire bent at various angles to provide for resistance to displacement both by resistance to deflection, that is, bending, and torsion of the wires of which they are comprised. Each of the several patented structures is alleged to provide certain advantages in manufacture, assembly, construction and performance over any others. The spring units of the instant invention are generally of the aforesaid kind and are considered to constitute an improvement of such prior structures in that they are sturdier, less liable to be permanently deformed by excessive loads, more readily attachable to the base and grid frame and are adaptable to provide support at the corners as well as along the sides and ends and intermediate the sides and ends. The bent wire springs as herein disclosed and the spring assemblies structured therefrom are economical in the use of wire, provide maximum stability and a firm and balanced yield.